Strange TPS/DME issues

[lowbob84]

So last week my car started idling funny. On start up it would settle in at about 850-900rpms. But then as I would drive along and come to a stop, if I was any where in the 1500-2000rpm range, the car would continue to idle at that level for several seconds and then drop to about 1000rpms and stay there.

So I searched the archives without much luck. I found a couple things saying it could be the TPS. So I went to Clark's Garage and Arnnworx to see what they have to say.

Here's what Clark has to say:



For turbocharged cars:

Disconnect the electrical connector for the DME control unit.


Connect an ohmmeter between terminal 2 on the DME wiring harness plug and ground. This will check the idle contact.
With the throttle closed, the ohmmeter should read between 0 - 10 ohms. With the throttle open, the ohmmeter should read infinite (∞). The switch in resistance must occur as soon as the throttle starts to open (approximately 1°).
Disconnect the electrical connector for the KLR control unit.
Connect an ohmmeter between terminals 22 and 23 on the KLR wiring harness plug. With the throttle closed, the ohmmeter should read between 320 - 670 ohms.
Slowly open the throttle to the wide open throttle (WOT) position. As the throttle opens, the resistance should continuously increase to full open resistance without any breaks. Full open resistance is 2.7 - 4.7 Kohms.

And Arnnworx says pretty much the same thing here:
http://www.arnnworx.com/tps-repair.htm

So I go through the steps except I cant get a reading on the DME from terminal 2. Now the Arnnworx page says if I can't get a reading to go straight to the TPS plug which I did (and it worked fine). So then they tell me to check the power to the number 2 terminal. How in the world to I check if there's power to the number 2 terminal? Thats where I'm stuck. So any help would be very much appreciated.

If anyone has any other suggestions, please let me know. On another note, the Arnnworx page has you check the throttle cut-off Valve:

3. Checking Throttle Valve Cut-Off

3.1 Pull plug off TPS and bridge Terminals 4 and 6 with auxiliary wire.

3.2 Start engine and increase speed to 1600 rpm. The motor should begin to surge.

Well my engine cuts back to idle after reaching 1600 rpms instead of surging. But from the valves name, it seems like it'd be more likely to drop rather than surge any ideas?

And lastly, if you look at the picture, there's an A plug and B plug coming off the DME plug. I don't have a B plug, and my A plug isn't plugged in to anything. Is that common on the 951, or is that another thing I need to run down.

TIA!

[nynor]

i'd say you have a vacuum leak or the throttle is sticking.

as for pin two, what have you tried? a multimeter might come in handy to see if there is voltage at pin two, while having the DME relay socket jumpered.

[lowbob84]

I'm fairly confident I don't have a vacuum leak. I have replaced the smaller lines with the Lindsey Racing Vacuum Line kit and I've replaced several of the larger lines when during my venturi delete last year.

As for pin two, I was supposed to measure resistance between pin 2 and ground. So I had my multimeter out there, but it just read 0. So the next step was to see if power was getting to pin 2.

So if I have a voltage at pin 2 after I jump the relay, is that going to tell me I have a bad relay?

[nynor]

sounds right. do you have a spare relay to try?

you could still have vacuum leaks. i found that three of the bolts holding the intake manifold to the head had worked a little loose.

[lowbob84]

Good point about the intake. I'll check to see if I can find anything with it tomorrow. I'm also thinking I'm going to supply 5V to the TPS itself and seeing if I can get a reading from it. I'm thinking maybe its broken and causing a short circuit which would give me a zero reading on the multimeter at the DME. Thanks for the input nynor!

[nynor]

as for other vacuum leaks, you can spray some starter fluid around the intake areas with the engine running. if the idle picks up, you have a vacuum leak.